For still photos, YES the Pixel 8 Pro will be better than the iPhone 15 Pro Max, for sure. Now videos, that always goes to the iPhone, and I would think the 15PM will still beat the 8P in taking videos, but for portrait shots, the Pixel hands down the winner. The Pixel 8 is supposed to get an upgraded new camera sensor, Google wants it to remain the photo king.
As far as the Tensor 3 and it being better than the T2, I'm not holding my breath for it being a night and day upgrade, I think it will realistically just be a bit better, rumors 15% to 20% better, but hopefully it is better in the efficiency department, giving better battery life and running cooler.
I might actually go with the the smaller Pixel 8 this time, as it will finally also have the 120hz display, and I'm starting to get sick of these giant smartphones, they're not easy for one handed use, I wouldn't mind a more pocket friendly easier to hold phone, the Pixel 8 will have a 6.1" screen, down from the Pixel 7 6.3" display.